The present invention relates to a wheel lock prevention device and in particular to wheel lock prevention device for motor vehicles comprising a relay valve having a primary side on which side the relay valve is actuated by pressurized air controlled via a brake valve which in turn is controlled by the motor vehicle operator. The relay valve also has a secondary side, from which side the pressure in a wheel brake cylinder is controlled by way of a double valve, the wheel brake cylinder being alternately connected via the double valve to a source of pressurized air or to an outside air connection.
A wheel lock prevention device of this type is known. The relay valves used in the known device are designed to allow the pressurized air controlled by the motor vehicle operator's brake valve to pass to the brake cylinder from a pressurized air supply proportionally over a large valve cross-section of the double valve.
A requirement of wheel lock prevention devices is rapid pressure reduction and short switching periods. However, with rapid pressure reduction, a synchronization difference is produced between the primary and secondary pressure. In the holding stage, the primary pressure controlled via the magnetic valves then determines the actual value of the holding pressure. Thus, the secondary pressure is always reduced by the amount of the synchronization difference and thus the braking force coefficient, that is, the ground adhesion of the wheel is not utilized efficiently.